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Provide REST Adapter for Compass Graphql API

Compass GraphQL API is not compatible with Application Connector REST API. To avoid rewriting integration layer for Application Connector clients, we can provide Adapter that translates Application Connector API to Compass API.

Reproducing tutorial steps

This section describes modifications required to ensure that the Application Connector tutorial still works.

  1. Create a new Application

In the former approach, the Application CR was created manually in a Runtime. In the new approach, Agent reads information from the Director and creates appropriate Application CRs. There is an open question, what should happen for manually created Application CRs. Right now, Agent ignores them completely.

  • If there is a requirement that manually created Application should be automatically registered in Compass, a new Controller has to be implemented.
  • If there is a requirement that manually created Application CR should be handled by the former services, this complicates the implementation as the status of TokenRequest will be populated differently, depending on whether the Application CR comes from Agent or was created manually.

AFAIK, creating an Application was a manual step usually performed in UI. Because of that, we should consider not introducing previously mentioned Controller, and just instruct Admins to create an Application using Compass UI.

  1. Get a client certificate

When creating a TokenRequest, the Controller updates the status and provides token and configuration URL fields. There is an open question, if we should support getting token by creating TokenRequest. If so, Agent should be responsible for setting the status of TokenRequest.

After calling the /v1/applications/signingRequests/info endpoint, the following data is returned:

{
    "csrUrl": "",
    "api":{
        "metadataUrl":      "",
        "eventsUrl":        "",
        "infoUrl":          "",
        "certificatesUrl":  "",
    },
    "certificate":{
        "subject":"OU=Test,O=TestOrg,L=Waldorf,ST=Waldorf,C=DE,CN={APP_NAME}",
        "extensions": "",
        "key-algorithm": "rsa2048",
    }
}

csrUrl should point to the Adapter's /v1/applications/certificates. certificate field is populated by Adapter by calling Connector's GraphQL configuration query.

  1. Register a service
curl -k --cert ./app1_client.crt   --key ./generated.key -X POST https://gateway.34.77.12.120.xip.io/app1/v1/metadata/services --data-binary "@serviceRegistrationManyAPIs.json"

{
  "provider":"SAP",
  "name":"api1",
  "description": "api1 desc",
  "shortDescription": "api1 short desc",
  "identifier": "api1Identifier",
  "labels":{
  	"label1":"value1",
  	"label2": "value2"
  },
  "api":{
  	"targetUrl":"http://some-app1.pl",
  	"requestParameters": {
  	  "headers": {
  	      "header1": "value1"
  	  }
  	}
  }

}

Compass equivalent: addApiDefinition or addEventDefinition

Challenges:

  • in the former API, there is a service which seems to be equivalent to API Package that is missing in Compass
  • identifier has no mapping in the Compass API
  • you cannot label ServiceClass using Compass API
  • specificationURL, specificationCredentials, specificationRequestParameters can be mapped to FetchRequest, but it is not yet implemented
  • quoting the documentation:

If the api.spec or api.specificationUrl parameters are not specified and the api.type parameter is set to OData, the Application Registry will try to fetch the specification from the target URL with the $metadata path.

Special handling for OData can be implemented in the Adapter (assuming that FetchRequest is implemented).

TODO:

  • CSRF tokens are not implemented in Compass
  • Documentation: in Compass, documentation can be added only on the Application level

Diagram

Kyma Integration Layer, implemented as a part of the external solution, reads the status of the TokenRequest that returns a URL pointing to Adapters. Adapters proxy calls to Compass components (REST --> GraphQL) and perform type conversions.

For the security model details see this document